Projector apparatus and projection image correcting program product

ABSTRACT

A projector apparatus includes: a projection unit that projects an image onto a projection surface; a reflectance distribution detection unit that detects a reflectance distribution at the projection surface; a density distribution detection unit that detects a density distribution of a base pattern on the projection surface; a smoothing unit that smooths the reflectance distribution and the density distribution; an input unit that inputs image data; a correction unit that corrects the input image data based upon the smoothed reflectance distribution and the smoothed density distribution; and a control circuit that controls the projection unit so as to project the image based upon the correction image data.

INCORPORATION BY REFERENCE

The disclosure of the following priority application is hereinincorporated by reference:

Japanese Patent Application No. 2009-095982 filed Apr. 10, 2009

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projector apparatus and a projectionimage correcting program.

2. Description of Related Art

Projectors, which are becoming increasingly compact and thus more mobileunits, are often used to project images onto projection surfaces otherthan screens, such as walls. However, the quality of an image projectedonto a colored or patterned projection surface is bound to be adverselyaffected by the color or the pattern at the projection surface. JapaneseLaid Open Patent Publication No. 2008-67080 and Japanese Laid OpenPatent Publication No. 2007-322671 each disclose a technology whereby animage corrected in correspondence to the reflectance distribution at theprojection surface is projected so as to render the color or the patternat the projection surface less noticeable in the projected image.

SUMMARY OF THE INVENTION

The technologies in the related art described above, adopted whencorrecting an input image, are yet to effectively address the followingissue. When an image is projected in an environment where ambient light(light other than the light originating from the projector apparatus) ispresent or an image is projected onto a projection surface at whichareas with extremely low reflectance, such as black streaks or spots,are present, the correction executed for the image before it isprojected onto the projection surface is bound to greatly lower thebrightness of the projection image. Such a reduction in the brightnessof the projection image will adversely affect the quality of theprojection image.

According to the 1st aspect of the present invention, a projectorapparatus comprises: a projection unit that projects an image onto aprojection surface; a reflectance distribution detection unit thatdetects a reflectance distribution at the projection surface; a densitydistribution detection unit that detects a density distribution of abase pattern on the projection surface; a smoothing unit that smoothsthe reflectance distribution and the density distribution; an input unitthat inputs image data; a correction unit that corrects the input imagedata based upon the smoothed reflectance distribution and the smootheddensity distribution; and a control circuit that controls the projectionunit so as to project the image based upon the correction image data.

According to the 2nd aspect of the present invention, it is preferredthat in the projector apparatus according to the 1st aspect, thecorrection unit alters a data size of the density distribution to a sizesmaller than the data size of the image that the projection unitprojects, and obtains through calculation correction information basedupon the reflectance distribution and the density distribution with thealtered data size, the correction information being used to cancel outan appearance of the base pattern on the projection surface.

According to the 3rd aspect of the present invention, it is preferredthat in the projector apparatus according to the 2nd aspect, thecorrection unit also generates a possible/impossible distribution imagebased upon the correction information, the image data input from theinput unit and the reflectance distribution, the possible/impossibledistribution image indicating a distribution of areas where theappearance of the base pattern on the projection surface may or may notbe cancelled out; the correction unit individually alters the data sizeof data constituting the possible/impossible distribution image and thedata size of the input image data each to a size smaller than the datasize of the image that the projection unit projects; and the correctionunit corrects the input image data by using the possible/impossibledistribution image with the altered data size, the input image with thealtered data size, the reflectance distribution and the correctioninformation.

According to the 4th aspect of the present invention, it is preferredthat in the projector apparatus according to the 2nd aspect, thecorrection unit obtains through calculation the correction informationfor each of specific areas defined on a projection image plane, basedupon the density distribution with the altered data size.

According to the 5th aspect of the present invention, it is preferredthat in the projector apparatus according to the 2nd aspect, thecorrection unit adjusts the density distribution based upon a largestvalue indicated in the density distribution with the altered data sizeso as to achieve a uniform density distribution over an entireprojection image plane, and obtains through calculation the correctioninformation for each of specific areas defined on a projection imageplane, based upon the uniform density distribution.

According to the 6th aspect of the present invention, it is preferredthat in the projector apparatus according to the 3rd aspect, thecorrection unit executes arithmetic operation needed for correction foreach of specific areas defined on a projection image plane, based uponthe possible/impossible distribution image with the altered data size.

According to the 7th aspect of the present invention, it is preferredthat in the projector apparatus according to the 3rd aspect, thecorrection unit adjusts the possible/impossible distribution based upona smallest value indicated in the possible/impossible distribution withthe altered data size so as to achieve a uniform possible/impossibledistribution over an entire projection image plane and executesarithmetic operation needed for correction based upon the uniformpossible/impossible distribution.

According to the 8th aspect of the present invention, acomputer-readable computer program product having included therein aprojection image correcting program that can be executed on a computer,with the projection image correcting program enabling the computer toexecute: detection processing through which a reflectance distributionat a projection surface is detected; density distribution detectionprocessing through which a density distribution of a base pattern on theprojection surface is detected; smoothing processing through which thereflectance distribution and the density distribution are smoothed;input processing through which image data are input; correctionprocessing through which the input image data are corrected based uponthe smoothed reflectance distribution and the smoothed densitydistribution; and projection processing through which an image basedupon the correction image data is projected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view of the projector apparatus achieved in anembodiment of the present invention.

FIG. 2 is a block diagram showing the structure adopted in the projectorapparatus.

FIG. 3 presents a flowchart of projection processing.

FIG. 4 presents a flowchart of processing that may be executed toanalyze the projection environment.

FIG. 5 presents a flowchart of processing that may be executed todetermine through calculation an ambient light pattern correction image.

FIG. 6 illustrates a smoothing process.

FIGS. 7A and 7B illustrate a blocking process, with FIG. 7A showing thepre-blocking state in FIG. 7B showing the post-blocking state.

FIGS. 8A and 8B illustrate expansion processing, with FIG. 8A showingthe state prior to execution of the expansion processing and FIG. 8Bshowing the state following the expansion processing.

FIG. 9 presents a flowchart of processing that may be executed togenerate a projection image.

FIGS. 10A and 10B illustrate the contraction processing, with FIG. 10Ashowing the state prior to execution of the contraction processing andFIG. 10B showing the state following the contraction processing.

FIG. 11 presents a flowchart of processing that may be executed togenerate a correction NG distribution image.

FIG. 12 is a schematic illustration presenting an example of an inputimage.

FIG. 13 is a schematic illustration presenting an example of an ambientlight pattern distribution image.

FIG. 14 is a schematic illustration presenting an example of areflectance distribution image.

FIG. 15 is a schematic illustration presenting an example of an ambientlight pattern distribution image.

FIG. 16 is a schematic illustration presenting an example of an imagethat may be obtained by smoothing the ambient light pattern distributionimage.

FIG. 17 is a schematic illustration presenting an example of an imagethat may result after the smoothed ambient light pattern distributionimage undergoes the blocking process.

FIG. 18 is a schematic illustration presenting an example of an imagethat may result from the expansion processing.

FIG. 19 is a schematic illustration presenting an example of an imagethat may result from re-smoothing.

FIG. 20 is a schematic illustration presenting an example of a targetambient light pattern image.

FIG. 21 is a schematic illustration presenting an example of an ambientlight pattern correction image.

FIG. 22 is a schematic illustration presenting an example of acorrection impossible distribution image.

FIG. 23 is a schematic illustration presenting an example of a smoothedcorrection impossible distribution image.

FIG. 24 is a schematic illustration presenting an example of acorrection impossible distribution image having undergone the blockingprocess.

FIG. 25 is a schematic illustration presenting an example of acorrection impossible distribution image having undergone thecontraction processing.

FIG. 26 is a schematic illustration presenting an example of are-smoothed correction impossible distribution image.

FIG. 27 is a schematic illustration presenting an example of a loweredbrightness distribution image.

FIG. 28 is a schematic illustration presenting an example of a targetprojection image.

FIG. 29 is a schematic illustration presenting an example of aprojection image.

FIG. 30 is a schematic illustration presenting an example of a correctedprojection image that is projected onto a projection surface.

FIG. 31 is a schematic illustration presenting an example of aprojection image projected onto a projection surface without correction.

FIG. 32 presents a flowchart of the processing executed in a variationto obtain through calculation an ambient light pattern correction image.

FIG. 33 presents a flowchart of the processing executed in a variationto generate a projection image.

FIG. 34 illustrates the overall structure of a system configured toprovide a program product.

DESCRIPTION OF PREFERRED EMBODIMENT

The following is a description of an embodiment of the presentinvention, given in reference to drawings. The projector apparatusaccording to the present invention corrects an input image incorrespondence to the conditions at the projection surface so as toimprove the appearance and the quality of the projected image.

FIG. 1 shows a projector apparatus 1 achieved in the embodiment of thepresent invention viewed from the front side. FIG. 1 shows a projectionlens 111A constituting a projection optical system 111 (see FIG. 2) anda photographic lens 121A constituting an imaging optical system 121 (seeFIG. 2), both disposed on the front side of the projector apparatus 1.The projector apparatus 1, placed on a desktop or the like, projects animage or the like from a built-in projection unit 110 (see FIG. 2)toward a screen or the like present in front thereof.

FIG. 2 is a block diagram showing an example of a structure that may beadopted in the projector apparatus 1. The projector apparatus 1 in FIG.2 includes the projection unit 110, an imaging unit 120, a controlcircuit 101, a memory 102, an operation unit 103, an external interface(I/F) circuit 104 and a memory card interface (I/F) 105. A memory card150 can be loaded at the memory card interface 105.

The control circuit 101 is constituted with a microprocessor and itsperipheral circuits. Based upon a control program stored in a built-inflash memory 101B, the control circuit 101 executes specific arithmeticoperations by using signals input thereto from various internal units inthe projector apparatus 1. The control circuit 101 outputs thearithmetic operation results as control signals to the individual unitswithin the projector apparatus 1 so as to control a projection operationand an imaging operation executed at the projector apparatus 1. It is tobe noted that the external interface (I/F) circuit 104 may be engaged incommunication with an external device to modify the control program anddata stored in the flash memory 101B or to store additional data intothe flash memory 101B.

An image processing unit 101A in the control circuit 101 executes imageprocessing for image data obtained via the external interface 104 orimage data obtained from the memory card 150. The image processingexecuted at the image processing unit 101A is to be described in detaillater.

The memory 102 is used as a work memory by the control circuit 101. Theoperation unit 103, constituted with buttons and switches, outputs tothe control circuit 101 an operation signal corresponding to a specificbutton or switch having been operated. Data can be written into, savedin and read out from the memory card 150 in response to instructionsissued by the control circuit 101.

The projection unit 110 includes the projection optical system 111, aliquid crystal panel 112, an LED light source 113 and a projectioncontrol circuit 114. The LED light source 113 illuminates the liquidcrystal panel 112 with luminance the level of which corresponds to asupplied current. At the liquid crystal panel 112, an optical image isgenerated in response to a drive signal provided from the projectioncontrol circuit 114. The projection optical system 111 projects theoptical image output from the liquid crystal panel 112. In response toan instruction issued by the control circuit 101, the projection controlcircuit 114 outputs control signals to the LED light source 113 and theliquid crystal panel 112.

The projection unit 110 projects a specific image indicated by thecontrol circuit 101. An image expressed with image data provided by anexternal device via the external interface circuit 104, as well as animage expressed with image data saved in the memory card 150, can beprojected by the projection unit 110. The term “input image” is used inthe description of the embodiment to refer to the image expressed withimage data saved in the memory card 150 or the image expressed withimage data provided by an external device via the external interfacecircuit 104.

The imaging unit 120, which includes the imaging optical system 121, animage sensor 122 and an imaging control circuit 123, captures an imageof the projection surface in response to an instruction issued by thecontrol circuit 101. The imaging optical system 121 forms a subjectimage on an imaging surface of the image sensor 122. The image sensor122 converts the subject image to electrical signals. The image sensor122 may be a CCD image sensor or a CMOS image sensor. The imagingcontrol circuit 123 controls the drive of image sensor 122 in responseto an instruction issued by the control circuit 101 and also executesspecific signal processing on the electrical signals output from theimage sensor 122.

Next, the input image correction processing executed in the projectorapparatus 1 is described. This correction processing is executed inorder to render less noticeable any pattern or stain on the projectionsurface, uneven illumination on the projection surface attributable toambient light or the like, that would otherwise stand out in theprojected image (projection image) as the input image is projected ontothe projection surface. The control circuit 101 executes the correctionprocessing based upon an image of the projection surface photographedvia the imaging unit 120.

(Projection Processing)

FIG. 3 presents a flowchart of the projection processing executed by thecontrol circuit 101. As a projection instruction is issued for theprojector apparatus 1, the control circuit 101 starts up a program basedupon which the processing in FIG. 3 is executed.

In step S21 in FIG. 3, the control circuit 101 analyzes the projectionenvironment. In more specific terms, the control circuit 101 engages theimaging unit 120 in operation to capture an image of the projectionsurface and then obtains through calculation a density distributionimage and an image indicating the reflectance distribution at theprojection surface. The density distribution image indicates thepresence of any pattern or stain on the projection surface and a stateof any uneven illumination over the projection surface attributable toambient light. This processing is to be described in detail later.

In step S22, the control circuit 101 obtains through calculation anambient light pattern correction image. The ambient light patterncorrection image (for instance, an image assuming a light/dark areadistribution in a phase that is the inverse of the light/dark areadistribution in the base pattern at the projection surface) is used tocancel out any pattern or stain present at the projection surfaceilluminated with the ambient light (light originating from a lightsource other than the projector apparatus 1) from the projection image.This processing, too, is to be described in detail later.

In step S23, the control circuit 101 reads the image data expressing aninput image via the external interface circuit 104 or from the memorycard 150 and stores the image data thus read into the memory 102. FIG.12 is a schematic illustration presenting an example of an input image.

In step S24, the control circuit 101 corrects the input image andobtains through calculation a projection image. In more specific terms,the control circuit 101 first creates a correction impossibledistribution image. The term “correction impossible distribution image”is used to refer to an image that indicates each area where the adverseeffect attributable to a base pattern or stain present at the projectionsurface cannot readily be canceled out in the projection image even byprojecting the image after correcting the input image in correspondenceto the reflectance at the projection surface, as in the related art. Thepresence of such an area where the adverse effect of a base pattern orstain at the projection surface cannot readily be canceled out in theprojection image is attributable to a lower level of reflectance in theparticular area at the projection surface. The control circuit 101 nextsmooths the correction impossible distribution image and then, basedupon the smoothed correction impossible distribution image and the imageindicating the projection surface reflectance, it corrects the imagehaving been read in step S23. The control circuit 101 further correctsthe input image having been corrected as described above to add theadverse effects of the ambient light by adding the ambient light patterncorrection image, having been obtained through calculation in step S22,to the corrected input image. It is to be noted that this processing,too, is to be described in detail later.

In step S25, the control circuit 101 executes analog conversion for theprojection image having been obtained through calculation (corrected) instep S24 (i.e., the image obtained by correcting the input image) andprojects via the projection unit 110 the image resulting from theconversion. In step S26, the control circuit 101 makes a decision as towhether or not there is another input image to be projected. Anaffirmative decision is made in step S26 if there is another input imageto be projected and the operation returns to step S23 in this case.However, if there is no image to be projected, a negative decision ismade in step S26 and the processing in FIG. 3 ends.

(Processing Executed to Analyze the Projection Environment)

In reference to the flowchart presented in FIG. 4, an example ofprocessing that may be executed in step S21 (see FIG. 3) to analyze theprojection environment is described in detail. The input image in theexample is expressed with R data, G data and B data, each assuming aneight-bit data structure, and the volume of the data expressing theinput image is equivalent to 1024 (across)×768 (down) pixels. However,the data bit length does not need to be eight bits and may be adjustedas necessary. Assuming that an image with the value at its ith pixelindicated as (R, G, B)_(i) is projected by the projection unit 110, thepixel value taken in the photographic image at the projection surface,which corresponds to the value at the ith pixel, is indicated as (R_(P),G_(P), B_(P))_(i) in the following description.

In step S31 in FIG. 4, the control circuit 101 projects a black image((R, G, B)_(i)=(0, 0, 0)_(i)) onto the projection surface from theprojection unit 110. In step S32, the control circuit 101 engages theimaging unit 120 to capture a photographic image of the projectionsurface onto which the black image is projected. It is to be noted thateven when a black image is projected via the projection unit 110, theoutput does not necessarily indicate exactly 0. In the description, suchas output is referred to as an unintended output from the projectionunit 110. The following explanation is provided by assuming that theambient light mentioned earlier includes the unintended output from theprojection unit 110.

In step S33, the control circuit 101 obtains through calculation animage (to be referred to as an ambient light pattern distribution imageA01) by using the photographic image captured via the imaging unit 120in step S32. Any base pattern, stain or the like present at theprojection surface, illuminated with the ambient light, i.e., lightoriginating from a light source other than the projector apparatus 1 andthe unintended output from the projection unit 110, shows up in thisimage. In other words, the ambient light pattern distribution image A01is equivalent to a density distribution image. The pixel value in theambient light pattern distribution image A01 is notated as; (R_(P),G_(P), B_(p))_(i)=(R_(A01), G_(A01), B_(A01))_(i). FIG. 13 is aschematic illustration presenting an example of the ambient lightpattern distribution image A01. FIG. 13 shows a base pattern and stainspresent at the projection surface illuminated with the ambient lightshowing up as a distribution of varying levels of density in the ambientlight pattern distribution image A01. In FIG. 13, dotted areas indicatedby reference numerals r1˜r8 are part of the base pattern at theprojection surface, whereas reference numeral r9 indicates a stain onthe projection surface. In addition, a shaded area rx is an area dimlyilluminated due to uneven illumination provided by the ambient light,whereas reference numeral ry indicates an area brightly illuminated dueto uneven illumination provided by the ambient light. It is to be notedthat the boundaries of the patterned areas r1, r2, r5, r6 and r8 areindicated with solid lines in FIG. 13 in order to simulate a conditionin which the boundaries of the base pattern portions r1, r2, r5, r6 andr8 are more noticeable than the boundaries of the base pattern portionsr3, r4 and r7.

In step S34, the control circuit 101 projects a white image ((R, G,B)_(i)=(255, 255, 255)_(i)) onto the projection surface from theprojection unit 110. “255” is equivalent to the maximum value that canbe indicated by the eight-bit data. In step S35, the control circuit 101engages the imaging unit 120 in operation to capture an image of theprojection surface onto which the white image is projected. The pixelvalue assumed in this photographic image A02 is indicated as; (R_(P),G_(P), B_(P))_(i)=(R_(A02), G_(A02), B_(A02))_(i). The base pattern andstains on the projection surface illuminated with the projection unit110 and the base pattern and stains on the projection surfaceilluminated with light originating from a light source other than theprojector apparatus 1 appear in the photographic image A02 obtained bycapturing an image of the projection surface onto which the white imageis projected as described above. To be more exact, the photographicimage A02 contains the base pattern and stains on the projection surfaceilluminated with ambient light, i.e., light originating from a lightsource other than the projector apparatus 1 and light unintentionallyoutput from the projection unit 110, as well as the base pattern andstains on the projection surface illuminated with the lightintentionally output from the projection unit 110.

In step S36, the control circuit 101 obtains through calculation animage (to be referred to as a reflectance distribution image A03)indicating the reflectance at the projection surface by determining thedifference between the photographic image A02 and the ambient lightpattern distribution image A01. In more specific terms, the controlcircuit 101 obtains the image through calculation expressed as;(R_(A03), G_(A03), B_(A03))_(i)=(R_(A02)−R_(A01), G_(A02)−G_(A02),B_(A02)−B_(A01))_(i). Thus, the reflectance distribution image A03obtained as a result is equivalent to an image showing the base patternand the stains on the projection surface illuminated with the lightintentionally output from the projection unit 110, i.e., an image fromwhich any influence of the ambient light illumination has beeneliminated. The reflectance distribution image A03 contains thereflectance at the projection surface, and also contains the influenceof any unevenness in the quantity of light output from the projectionunit 110. Once the reflectance distribution image A03 is obtainedthrough calculation, the control circuit 101 ends the processing shownin FIG. 4. FIG. 14 is a schematic illustration presenting an example ofthe reflectance distribution image A03. FIG. 14 shows a linear area r9with low reflectance (e.g., a mark on the projection surface) and basepattern portions r1˜r8. Through subsequent processing, various types ofimages, to be used for purposes of correction, are generated by usingthe reflectance distribution image A03 that also reflects the influenceof the unevenness in the quantity of light provided from the projectionunit 110, as described above, so as to also correct the adverse effectof the unevenness in the quantity of light provided by the projectionunit 110 without having to execute any special processing.

(Processing Executed to Obtain Ambient Light Pattern Correction ImageThrough Calculation)

In reference to the flowchart presented in FIG. 5, the processingexecuted in step S22 (see FIG. 3) mentioned earlier to obtain throughcalculation the ambient light pattern correction image is described indetail.

In step S41 in FIG. 5, the control circuit 101 culls some of the pixelsconstituting the ambient light pattern distribution image A01. Assumingthat the initial ambient light pattern distribution image A01 isconstituted with 1024 (across)×768 (down) pixels, the control circuit101 obtains an ambient light pattern distribution image a01 with areduced size of 256×192 pixels by culling the data to ¼ both across anddown. FIG. 15 is a schematic illustration presenting an example of theambient light pattern distribution image a01. As in the ambient lightpattern distribution image A01 in FIG. 13, the base pattern portionsr1˜r8 and the mark r9 at the projection surface, and the area rx dimlyilluminated and the area rx brightly illuminated due to unevenillumination by ambient light all appear in the ambient light patterndistribution image a01. However, since the data have been culled to ¼across and down, the mark r9 shows up as a disrupted line, unlike thecontinuous line appearing in the ambient light pattern distributionimage A01. Accordingly, the mark r9 is schematically indicated as adotted line in FIG. 15.

In step S42, the control circuit 101 executes low pass filter processing(e.g., moving average processing) in order to smooth the reduced ambientlight pattern distribution image a01. In reference to FIG. 6, theprinciple of smoothing processing executed over a 3×3 kernel (a localarea used for weighted averaging) is described as an example. FIG. 6shows a target pixel assuming the central position in the group of 3×3pixels, with an ambient light pattern distribution value of 0.3indicated at the target pixel. It is to be noted that the term “ambientlight pattern distribution value” is used to refer to the pixel valueindicated at the reduced ambient light pattern distribution image a01.Pixels adjacent to the target pixel individually indicate ambient lightpattern distribution values of 1.0, 0.8, 1.0, 0.6, 0.5, 0.5, 0.7 and0.9. The control circuit 101 executes weighted averaging calculation byusing the ambient light pattern distribution value at the target pixeland the ambient light pattern distribution values at the pixels adjacentto the target pixel. Namely, the control circuit 101 adds up the ambientlight pattern distribution value at the target pixel and the ambientlight pattern distribution values at the pixels adjacent to the targetpixel with a weight of 1/9 applied thereto. The ambient light patterndistribution value calculated by the control circuit 101 for thesmoothed target pixel is 0.7. FIG. 16 presents an example of an imagethat may be obtained by smoothing the ambient light pattern distributionimage a01. Through the smoothing processing, the boundaries of the areascorresponding to the base pattern portions and the stains at theprojection surface are rendered less noticeable. FIG. 16 schematicallyillustrates how the boundaries have become less noticeable with theboundaries of the base pattern portions r1, r2, r5, r6 and r8 indicatedwith a one-point chain lines and the mark r9 indicated as a dotted line.

It is to be noted that size of the kernel is allowed to assume theoptimal size to assure the best appearance for the corrected input imagewhen it is projected. For instance, the kernel may assume a 9×9 arealsize or a 13×13 areal size. In addition, instead of smoothing the imagethrough a low pass filter, the control circuit 101 may smooth the imagethrough a median filter.

In step S43, the control circuit 101 divides the ambient light patterndistribution image having undergone the smoothing processing intoblocks. In the following description, the ambient light patterndistribution image that has been smoothed is referred to as a smoothedambient light pattern distribution image. When dividing the smoothedambient light pattern distribution image into blocks, the controlcircuit 101 first partitions the smoothed ambient light patterndistribution image into specific areas. The control circuit 101 thendesignates the largest smoothed ambient light pattern distribution valueamong the smoothed ambient light pattern distribution values indicatedat the pixels present in each partitioned area (each block) as asmoothed ambient light pattern distribution value representing all thepixels in the area (block). It is to be noted that the term “smoothedambient light pattern distribution value” is used to refer to the pixelvalue indicated in the smoothed ambient light pattern distributionimage.

In reference to FIGS. 7A and 7B, an example of block processing in whicha 4×4 pixel area is processed as a single block is described. As shownin FIG. 7A, the largest smoothed ambient light pattern distributionvalue among the pixel values indicated at the 4×4 pixels, i.e., in theparticular block, is 1.0. Accordingly, all the pixels in the blockhaving undergone the block processing assume a smoothed ambient lightpattern distribution value of 1.0, as shown in FIG. 7B. Through thisblock processing, the size of the smoothed ambient light patterndistribution image is altered to 64×48 pixels. FIG. 17 is a schematicillustration presenting an example of an image that may be obtained byexecuting the block processing on the smoothed ambient light patterndistribution image. FIG. 17 indicates how the shapes of the areas in theimage corresponding to the base pattern and stains on the projectionsurface may change and the boundaries, having been rendered lessnoticeable through the smoothing processing described earlier, maychange as a result of the block processing. FIG. 17 schematicallyillustrates how the boundaries have been rendered less visible by usingdots identical to the dots indicating the area ry and the base patternportions r3, r4 and r7 and the mark r9. In addition, the boundaries ofthe base pattern portions r1, r2, r5, r6 and r8, having been alteredfrom the state shown in FIG. 16, have become more noticeable. FIG. 17schematically illustrates how the boundaries have changed by indicatingthe boundaries of the base pattern portions r1, r2, r5, r6 and r8 withtwo-point chain lines.

In step S44, the control circuit 101 executes expansion processing onthe smoothed ambient light pattern distribution image having undergonethe block processing. In the expansion processing, the control circuit101 first sets a kernel assuming a specific range centered on the targetpixel in the smoothed ambient light pattern distribution image. Thecontrol circuit 101 then alters the ambient light pattern distributionvalues at the individual pixels present within the kernel to the largestvalue among the ambient light pattern distribution values indicatedwithin the particular kernel. In reference to FIGS. 8A and 8B, anexample of expansion processing that may be executed by the controlcircuit 101 over a 3×3 kernel range (pixel range) is described. Byadjusting all the ambient light pattern distribution values within the3×3 kernel range shown in FIG. 8A to the largest pixel value, a smoothedambient light pattern distribution image having undergone the expansionprocessing, such as that shown in FIG. 8B, is obtained. The controlcircuit 101 in the embodiment, repeatedly executes the expansionprocessing twice. FIG. 18 is a schematic illustration presenting anexample of an image that may result from the expansion processing. Theimage having undergone the expansion processing will assume wider rangesin correspondence to the largest values. FIG. 18 schematicallyillustrates the results of the expansion processing by using dots toindicate the boundaries of the base pattern portions r1, r2, r5, r6 andr8.

In step S45, the control circuit 101 further smooths the smoothedambient light pattern distribution image having undergone the expansionprocessing. The control circuit 101 may smooth the image through movingaverage processing executed over, for instance, a 9×9 kernel. FIG. 19 isa schematic illustration presenting an example of an image that mayresult from the further smoothing processing. Through the furthersmoothing processing, the boundaries of the areas corresponding to thebase pattern portions on the projection surface, which have beenrendered noticeable again as a result of the expansion processing,become less visible. FIG. 19 schematically illustrates how theboundaries of the base pattern portions r1, r2, r5, r6 and r8 havebecome less noticeable by indicating them with fewer dots than in FIG.18. In step S46, the control circuit 101 generates a target ambientlight pattern image through enlargement processing. In more specificterms, the control circuit 101 enlarges the smoothed 64×48 pixel imagethrough a bilinear method and obtains a 1024×768 pixel image (referredto as a target ambient light pattern image E01). The target ambientlight pattern image E01 thus generated is equivalent to an imageobtained by extracting a low frequency component contained in theambient light pattern distribution image A01. FIG. 20 presents anexample of the target ambient light pattern image E01.

In step S47, the control circuit 101 obtains through calculation anambient light pattern correction image D01 by subtracting the ambientlight pattern distribution image A01 from the target ambient lightpattern image E01. More specifically, the control circuit 101 obtainsthe image through calculation expressed as; (R_(D01), G_(D01),B_(D01))_(i)=(R_(E01)−R_(A01), G_(E01)−G_(A01), B_(E01)−B_(A01),)_(i).The resulting ambient light pattern correction image D01 is equivalentto an image obtained by extracting a high frequency component from theambient light pattern distribution image A01. The ambient light patterncorrection image D01 indicates the quantity of light required at theprojection surface in order to enable the viewer to see the projectionimage unaffected by any adverse effects of the base pattern or stains onthe projection surface. In other words, the ambient light patterncorrection image D01 represents the quantity of light perceived by theviewer.

In step S48, the control circuit 101 obtains through calculation anambient light pattern correction image F01 having undergone reflectancecorrection by dividing the ambient light pattern correction image D01 bythe reflectance distribution image A03. More specifically, the controlcircuit 101 obtains the image through calculation expressed as (R_(F01),G_(F01), B_(F01))_(i)=(R_(D01)/R_(A03), G_(D01)/G_(A03),B_(D01)/B_(A03))_(i). It then the processing in FIG. 5. FIG. 21 presentsan example of the ambient light pattern correction image F01.

The ambient light pattern correction image F01 indicates the outputprovided from the projection unit 110, i.e., the quantity of lightoutput from the projection unit 110 in order to project the projectionimage. However, since the light from the projection unit 110 isperceived by the viewer at the projection surface, where the quantity oflight is altered in correspondence to the reflectance thereat, thequantity of light perceived by the viewer does not match the quantity ofthe output from the projection unit 110. Namely, the quantity of lightperceived by the viewer matches the value obtained by multiplying thequantity of light originating from the projection unit 110 by thereflectance at the projection surface. As explained earlier, thereflectance at the projection surface is indicated by the reflectancedistribution image A03, whereas the quantity of light perceived by theviewer is indicated by the ambient light pattern correction image D01.Accordingly, the control circuit 101 obtains through calculation theambient light pattern correction image F01 indicating the quantity oflight output from the projection unit 110 by dividing the ambient lightpattern correction image D01 by the reflectance distribution image A03.

(Projection Image Generation Processing)

In reference to the flowchart presented in FIG. 9, an example ofprocessing that may be executed in step S24 (see FIG. 3) to generate theprojection image is described in detail.

In step S51 in FIG. 9, the control circuit 101 obtains an image(hereafter referred to as a linearized image C01) by individuallylinearizing the pixel values indicated in the input image (1024×768pixels). The control circuit 101 may calculate linearized values by, forinstance, sequentially executing a pixel-by-pixel inverse γ conversionin reference to a lookup table (LUT). Such an LUT should be stored inthe flash memory 101B.

In step S52, the control circuit 101 culls some of the pixelsconstituting the linearized image C01. Namely, the control circuit 101obtains a linearized image c01 with a reduced size of 256×192 pixels byculling the data to ¼ the initial pixel size (1024×768) both across anddown.

In step S53, the control circuit 101 creates a correction impossibledistribution image B03, and then the operation proceeds to step S54. Theprocessing executed to create the correction impossible distributionimage B03 is to be described in detail later. It is to be noted that thecorrection impossible distribution image B03 is an image indicating thedistribution of areas where the base pattern or stains on the projectionsurface cannot be canceled out of the projection image due to lowreflectance at the projection surface, as explained earlier.

In step S54, the control circuit 101 culls some of the pixelsconstituting the correction impossible distribution image B03 to ¼ ofthe current size both across and down so as to obtain a correctionimpossible distribution image b03 with a reduced size of 256×192 pixelsand then smooths the correction impossible distribution image b03. FIG.22 presents an example of the correction impossible distribution imageb03. Reference numerals r9˜r14 in FIG. 22 each indicate an area thatcannot be corrected without lowering the brightness. The correctionimpossible distribution image b03 assumes a darker shade over an areawith a higher level of difficulty for correction. FIG. 22 assumes ahigher level of dot density in the areas r9˜r14 to indicate a higherlevel of correction difficulty. Namely, the level of correctiondifficulty is higher in the areas r10˜r13 in FIG. 22.

FIG. 23 is a schematic illustration presenting an example of acorrection impossible distribution image having undergone smoothingprocessing. It is to be noted that the control circuit 101 smooths theimage through moving average processing executed over, for instance, a3×3 kernel. FIG. 23 schematically illustrates how the boundaries of theareas r10˜r14, which cannot be corrected without lowering thebrightness, have become less noticeable. In addition, the area r9indicated as a line in FIG. 22 is represented with dots in FIG. 23 toindicate that it has been smoothed.

In step S55, the control circuit 101 divides the smoothed correctionimpossible distribution image into blocks. Assuming that the smoothedcorrection impossible distribution image is divided into blocks eachmade up with 4×4 pixels, the control circuit 101 designates the largestpixel value among the pixel values indicated at the pixels contained ineach block as a correction impossible distribution value for the entireblock in the block processing. Through the block processing, thecorrection impossible distribution pixel is converted to an imageconstituted with 64×48 pixels. FIG. 24 is a schematic illustrationpresenting an example of a correction impossible distribution image thatmay result from the block processing. FIG. 24 schematically illustrateshow the shapes of the areas r9˜r14 have been altered through the blockprocessing. In addition, FIG. 24 indicates that the alterations in theshapes of the individual areas r9˜r14 attributable to the blockprocessing have resulted in the areas r9 and r10 joining each other toform a substantially single area.

In step S56, the control circuit 101 executes contraction processing onthe correction impossible distribution image having undergone the blockprocessing. In the contraction processing, the control circuit 101 firstsets a kernel assuming a specific range centered on the target pixel inthe correction impossible distribution image having undergone the blockprocessing. Next, the circuit 101 designates the smallest value amongthe pixel values indicated at the pixels in the kernel as a correctionimpossible distribution value for the entire kernel. In reference toFIGS. 10A and 10B, an example of contraction processing that may beexecuted by the control circuit 101 over a 3×3 kernel range (pixelrange) is described. By adjusting all the pixel values within the 3×3kernel range shown in FIG. 10A to the smallest value, a correctionimpossible distribution image having undergone the contractionprocessing, such as that shown in FIG. 10B, is obtained. The controlcircuit 101 in the embodiment repeatedly executes the contractionprocessing twice. FIG. 25 is a schematic illustration presenting anexample of an image that may result from the contraction processing. Thecorrection impossible distribution image having undergone thecontraction processing will assume wider ranges in correspondence to thesmallest values. FIG. 25 schematically illustrates the results of thecontraction processing by indicating the areas r9˜r14 in shapes alteredfrom those of the areas r9˜r14 in FIG. 24.

In step S57, the control circuit 101 obtains a lowered brightnessdistribution image by further executing smoothing processing andenlargement processing on the correction impossible distribution imagehaving undergone the contraction processing. The control circuit 101smooths the image through moving average processing executed over, forinstance, a 9×9 kernel. FIG. 26 is a schematic illustration presentingan example of a correction impossible distribution image that may resultfrom the further smoothing processing. Through the further smoothingprocessing, the boundaries of the areas r9˜r14 in the image, which havebeen rendered noticeable again as a result of the block processing,become less visible. FIG. 26 schematically illustrates the results ofthe contraction processing by showing the areas r9˜r14 in shapes alteredfrom those of the areas r9˜r14 in FIG. 25.

In the enlargement processing, the control circuit 101 enlarges thefurther smoothed 64×48 pixel image through a bilinear method and obtainsa 1024×768 pixel image (referred to as a lowered brightness distributionimage H01). The lowered brightness distribution image H01 thus generatedis equivalent to an image obtained by extracting a low frequencycomponent contained in the correction impossible distribution image B03.FIG. 27 presents an example of the lowered brightness distribution imageH01. FIG. 27 schematically illustrates the results of the enlargementprocessing by showing the areas r9˜r14 in shapes altered from those ofthe areas r9˜r14 in FIG. 26. The lowered brightness distribution imageH01 indicates the distribution of areas assuming non-uniform lowbrightness levels on the projection surface (i.e., the base pattern andstains).

In step S58, the control circuit 101 obtains through calculation atarget projection image J01 by multiplying the linearized image C01 bythe lowered brightness distribution image H01 and then the operationproceeds to step S59. FIG. 28 is a schematic illustration presenting anexample of the target projection image J01. FIG. 28 schematicallyillustrates the target projection image J01 by superimposing the loweredbrightness distribution image H01 in FIG. 27 over the linearized imageC01.

The projection image seen by the viewer is an image perceived as theprojection image output from the projection unit 110, which is affectedto an extent corresponding to the reflectance at the projection surface,i.e., an image obtained by multiplying the projection image output fromthe projection unit by the reflectance distribution image A03. Providedthat the linearized image C01 is reproduced exactly as is on theprojection surface, the projected image can be viewed as a projectionimage unaffected by the base pattern, stains and the like on theprojection surface. In other words, only if the linearized image C01exactly matches the image obtained by multiplying an image (correctedimage) resulting from a specific correction of the linearized image C01by the reflectance, a projection image can be viewed free from anyadverse effects of the base pattern, stains and the like on theprojection surface. This means that the correction image can begenerated by dividing the linearized image C01 by the reflectancedistribution image A03. The correction image thus obtained is theprojection image that should be output from the projection unit 110 inorder to cancel out the appearance of the adverse effects of the basepattern, stains and the like on the projection surface. The correctionimage indicates that an area corresponding to an area with lowreflectance on the projection surface (an area greatly affected by thebase pattern, a stain or the like) is projected with a higher level ofbrightness (high brightness) in correspondence to the lower reflectance.

However, if the input image (or the linearized image C01) assumes largepixel values or if the reflectance at the projection surface is low, thepixel values in the correction image may exceed the level of the maximumoutput at the projection unit 110. In such a case, the control circuit101 should lower the brightness of the linearized image C01 so as toensure that the base pattern and stains on the projection surface, whichwould otherwise be visible in the projection image, can be corrected atthe maximum output level of the projection unit 110. At this time, inorder to ensure that the entire area (including areas less affected bythe base pattern or stains) of the linearized image will not beunnecessarily darkened as the brightness of the linearized image C01 isuniformly lowered, the control circuit 101 multiplies the linearizedimage C01 by the lowered brightness distribution image H01. The targetprojection image J01 is thus generated by adjusting the luminance(brightness) of areas in the linearized image C01, which correspond toareas greatly affected by the base pattern, stains and the like on theprojection surface, to a low level. This target projection image J01 isthe projection image seen by the viewer, which is not affected by thebase pattern, stains and the like on the projection surface.

In step S59, the control circuit 101 obtains through calculation atarget projection image K01 resulting from reflectance correction bydividing the target projection image J01 by the reflectance distributionimage A03 and then the operation proceeds to step S60. Morespecifically, the control circuit 101 obtains the image throughcalculation expressed as; (R_(K01), G_(K01),B_(K01))_(i)=(R_(J01)/R_(A03), G_(J01)/G_(A03), B_(J01)/B_(A013))_(i).

The target projection image K01 represents the projection image to beoutput by the projection unit 110. However, since the projection imageoutput from the projection unit 110 is altered in correspondence to thereflectance at the projection surface as seen by the viewer, theprojection image output from the projection unit 110 is not exactly thesame as the projection image seen by the viewer. Namely, the projectionimage seen by the viewer is equivalent to the product obtained bymultiplying the projection image output from the projection unit 110 bythe reflectance at the projection surface. As explained earlier, thereflectance at the projection surface is indicated in the reflectancedistribution image A03 and the image seen by the viewer is the targetprojection image J01. Accordingly, the control circuit 101 obtainsthrough calculation the target projection image K01, i.e. the projectionimage to be output from the projection unit 110, by dividing the targetprojection image J01 by the reflectance distribution image A03.

In step S60, the control circuit 101 obtains through calculation aprojection image L01 by adding the ambient light pattern correctionimage F01 to the target projection image K01 resulting from thereflectance correction and then the operation proceeds to step S61. Inmore specific terms, the control circuit 101 obtains the image throughcalculation expressed as; (R_(L01), G_(L01),B_(L01))_(i)=(R_(K01)+R_(F01), G_(K01)+G_(F01), B_(K01)+B_(F01))_(i).FIG. 29 is a schematic illustration presenting an example of theprojection image L01.

In step S61, the control circuit 101 obtains the actual projection imageL01 converted back to the nonlinear data format through γ conversionexecuted on the projection image L01. The γ conversion should beexecuted by using an LUT stored in the flash memory 101B.

(Correction Impossible Distribution Image Generation Processing)

In reference to the flowchart presented in FIG. 11, an example ofprocessing that may be executed in step S53 (see FIG. 9) when creatingthe correction impossible distribution image B03 is described in detail.In step S71 in FIG. 11, the control circuit 101 calculates the output(the quantity of light) from the projection unit 110 that can be used inthe input image correction. In more specific terms, assuming that theoutput of the projection unit 100 is 255, representing the maximumoutput value corresponding to 8-bit data, the control circuit 101subtracts the pixel value in the ambient light pattern correction imageF01 from 255 as expressed; (R_(M1), G_(M1), B_(M1))_(i)=(255−R_(F01),255−G_(F01), 255−B_(F01))_(i). The light output from the projection unit110 includes the light used to cancel out the appearance of the basepattern, stains and the like on the projection surface from theprojection image and the light used to project the image. In otherwords, only the light that is not used for canceling out the appearanceof the base pattern, stains and the like on the projection surface canbe used to project the image. Accordingly, the control circuit 101subtracts the pixel value in the ambient light pattern correction imageF01 corresponding to the quantity of light used to cancel the appearanceof the base pattern, stains and the like on the projection surface fromthe maximum output value. The value (R_(m1), G_(M1), B_(M1))_(i) thuscalculated, representing the quantity of light that can be used toproject the image, is to be referred to as an available-for-projectionlight quantity.

In step S72, the control circuit 101 calculates the quantity of light tobe output for purposes of eliminating (canceling) the appearance of thebase pattern, stains and the like on the projection surface. Morespecifically, the control circuit 101 executes calculation expressed as;(R_(N1), G_(N1), B_(M1))_(i)=(R_(C01)/R_(A03), G_(C01)/G_(A03),B_(C01)/B_(A03))_(i) by dividing the linearized image C01 by thereflectance distribution image A03. As described earlier, the projectionunit 100 projects an image obtained by dividing the linearized image C01by the reflectance distribution image A03 as the projection image. Inother words, in the image projected by the projection unit 110, an areacorresponding to an area on the projection surface with low reflectance(an area greatly affected by the base pattern, a stain or the like) isprojected with higher luminance (higher brightness) in correspondence tothe lower reflectance. Thus, (R_(N1), G_(N1), B_(N1))_(i) calculated asdescribed above represents the quantity of light that should be outputfrom the projection unit 110 in order to eliminate (cancel) theappearance of the base pattern, stains and the like on the projectionsurface. The value represented by (R_(N1), G_(N1), B_(N1))_(i) is to bereferred to as the required-for-projection light quantity.

In step S73, the control circuit 101 sequentially compares theavailable-for-projection light quantity and the required-for-projectionlight quantity, pixel by pixel. If “available-for-projection lightquantity”>“required-for-projection light quantity”, i.e., if (R_(M1),G_(M1), B_(M1))_(i)>(R_(N1), G_(N1), B_(N1))_(i) is true, the controlcircuit 101 makes an affirmative decision in step S73 and the operationproceeds to step S74A. However, if the “available-for-projection lightquantity” is not greater than the “required-for-projection lightquantity”, i.e., if (R_(M1), G_(M1), B_(M1))_(i)>(R_(N1), G_(N1),B_(N1))_(i) is not true, a negative decision is made in step S73 and theoperation proceeds to step S74B.

In step S74A, the control circuit 101 sets the correction impossibledistribution value so that (R_(B01), G_(B01), B_(B01))_(i)=(255, 255,255), before the operation proceeds to step S75. In step S74B, thecontrol circuit 101 sets the correction impossible distribution value sothat (R_(B01), G_(B01), B_(B01))_(i)=(R_(M1)/R_(N1), G_(M1)/G_(N1),B_(M1)/RB_(N1))_(i)×255, before the operation proceeds to step S75.

In step S75, the control circuit 101 makes a decision as to whether ornot the comparison in step S73 has been executed for all the pixelsconstituting the input image. An affirmative decision is made in stepS75 if the comparison in step S73 has been executed for all the pixelsconstituting the input image and in this case, the correction impossibledistribution calculation processing in FIG. 11 ends. If, on the otherhand, there is any pixel among the pixels constituting the input imagefor which the comparison in step S73 has not been executed, a negativedecision is made in step S75 and the operation returns to step S73.

FIG. 30 presents an example of a projection image that may be projectedonto the projection surface after undergoing the correction at theprojector apparatus 1 as described above. The appearance of the patternon the projection surface is rendered less visible. FIG. 31 presents,for purposes of comparison, an example of a projection image that may beprojected directly onto the projection surface without the correctingthe input image as described above. Unlike the projection image in FIG.30, the base pattern on the projection surface shows up in theprojection image in FIG. 31.

The following advantages are achieved through the embodiment describedabove.

(1) The projector apparatus 1 includes the projection unit 110 thatprojects an image onto a projection surface, the memory card I/F 105 viawhich image data are input and the control circuit 101. The controlcircuit 101 detects a projection surface reflectance distribution imageA03 and also detects a projection surface ambient light patterndistribution image A01. The control circuit 101 smooths the reflectancedistribution image A03 and the ambient light pattern distribution imageA01 and corrects image data C01 having been input based upon thesmoothed reflectance distribution image and the smoothed ambient lightpattern distribution image. The control circuit 101 then controls theprojection unit 110 so as to project an image based upon the correctionimage data. As a result, the input image can be corrected so as tocancel out the appearance of color on the projection surface and anystains or base pattern that may be present on the projection surfacewithout greatly compromising the quality of the projection image. Inaddition, through the smoothing processing, the input image can becorrected so that the corrected areas remain inconspicuous.

(2) The control circuit 101 alters the data size of the ambient lightpattern distribution image A01 to a size smaller than the data size ofthe image that the projection unit 110 projects. Then, based upon thereflectance distribution and the ambient light pattern distributionimage with the altered data size, the control circuit 101 obtainsthrough calculation correction information (ambient light patterncorrection image) to be used to cancel out the appearance of theprojection surface base pattern from the projection image. Through thesemeasures, the onus of the calculation processing can be lessenedcompared to that of the calculation executed without altering the datasize and consequently, the processing can be completed over a shorterperiod of time.

(3) The control circuit 101 generates a lowered brightness distributionimage H01 that indicates possible/impossible distribution of image areaswhere the appearance of the base pattern or stains on the projectionsurface may or may not be successfully canceled out, based upon thecorrection information (ambient light pattern correction image) F01, theinput image data C01 and the reflectance distribution A03. The controlcircuit 101 individually alters the data size of the lowered brightnessdistribution image H01 and the data size of the input image data C01each to a size smaller than the data size of the image that theprojection unit 110 projects. The control circuit 101 then corrects theinput image C01 by using the lowered brightness distribution image withthe altered data size, the input image with the altered data size, thereflectance distribution and the correction information (ambient lightpattern correction image). Through these measures, the onus of thecalculation processing can be lessened compared to that of thecalculation executed without altering the data sizes and consequently,the processing can be completed over a shorter period of time.

(4) The control circuit 101 obtains through calculation correctioninformation (ambient light pattern correction image) based upon thedensity distribution having undergone the size alteration, incorrespondence to each of specific areas defined on the projection imageplane. Thus, the projection image can be corrected in units ofindividual pixels by setting the specific areas each in correspondenceto a pixel so as to obtain the correction information for the particularpixel.

(5) The control circuit 101 executes the arithmetic operation necessaryfor correction based upon the lowered brightness distribution imagehaving undergone the size alteration, in correspondence to each ofspecific areas defined on the projection image plane. Thus, theprojection image can be corrected in units of individual pixels byexecuting the arithmetic operation for each of the pixels set as thespecific areas.

(Variation 1)

While the projection surface reflectance distribution is detected byobtaining through calculation an image indicating the projection surfacereflectance distribution in the embodiment described above, theprojection surface reflectance distribution may be detected through amethod other than that adopted in the embodiment. For instance, thecontrol circuit 101 may detect the reflectance distribution based uponthe intensity of the light projected from the projection unit 110 andthe intensity of the light reflected from the projection surface, whichis detected via the imaging unit 120.

(Variation 2)

While the description is given above in reference to the embodiment onan example in which varying correction quantities can be set within theimage plane, the present invention may be adopted in uniform correctionexecuted by setting a uniform correction quantity for the whole imageplane. In such a case, the control circuit 101 should execute theprocessing in the flowchart presented in FIG. 32 instead of theprocessing in the flowchart in FIG. 5 and should also execute theprocessing in the flowchart presented in FIG. 33 instead of theprocessing in the flowchart in FIG. 9.

(Processing Executed to Obtain Ambient Light Pattern Correction ImageThrough Calculation)

In reference to the flowchart presented in FIG. 32, the processingexecuted in step S22 (see FIG. 3) mentioned earlier to obtain throughcalculation the ambient light pattern correction image is described indetail.

In step S81 in FIG. 32, the control circuit 101 culls some of the pixelsconstituting the ambient light pattern distribution image A01. Assumingthat the initial ambient light pattern distribution image A01 isconstituted with, for instance, 1024 (across)×768 (down) pixels, thecontrol circuit 101 obtains an ambient light pattern distribution imagea01 with a reduced size of 256×192 pixels by culling the data to ¼ bothacross and down. FIG. 15 presents an example of the ambient lightpattern distribution image a01.

In step S82, the control circuit 101 executes low pass filter processing(e.g., moving average processing) in order to smooth the reduced ambientlight pattern distribution image a01. FIG. 16 presents an example of animage that may be obtained by smoothing the ambient light patterndistribution image a01.

It is to be noted that as explained earlier in reference to theembodiment, the size of the kernel may be adjusted as necessary and thesmoothing processing may be executed by using a median filter instead ofa low pass filter.

In step S83, the control circuit 101 determines the largest valueindicated in the smoothed ambient light pattern distribution image. Inother words, the control circuit 101 obtains the largest smoothedambient light pattern distribution value in the overall image. In stepS84, the control circuit 101 obtains through calculation an ambientlight pattern correction image DD01 by subtracting the ambient lightpattern distribution image A01 from the largest value. In more specificterms, the control circuit 101 obtains the image through calculationexpressed as; (R_(DD01), G_(DD01), B_(DD01))_(i)=(R_(max)−R_(A01),G_(max)−G_(A01), B_(max)−B_(A01))_(i). It is to be noted that (R_(max),G_(max), B_(max)) above represents the largest value.

In step S85, the control circuit 101 obtains through calculation anambient light pattern correction image FF01 having undergone reflectancecorrection by dividing the ambient light pattern correction image DD01by the reflectance distribution image A03. More specifically, thecontrol circuit 101 obtains the image through calculation expressed as;(R_(FF01), G_(FF01), B_(FF01))_(i)=(R_(DD01)/R_(A03), G_(DD01)/G_(A03),B_(DD01)/B_(A03))_(i), before ending the processing in FIG. 32.

(Projection Image Generation Processing)

In reference to the flowchart presented in FIG. 33, an example ofprocessing that may be executed in step S24 (see FIG. 3) to generate theprojection image is described in detail.

In step S91 in FIG. 33, the control circuit 101 obtains an image(hereafter referred to as a linearized image C01) by individuallylinearizing the pixel values indicated in the input image (e.g.,1024×768 pixels). The control circuit 101 may calculate linearizedvalues by, for instance, sequentially executing a pixel-by-pixel inverseγ conversion in reference to a lookup table (LUT). Such an LUT should bestored in the flash memory 101B.

In step S92, the control circuit 101 culls some of the pixelsconstituting the linearized image C01. Namely, the control circuit 101obtains a linearized image c01 with a reduced size of 256×192 pixels byculling the data to ¼ the initial pixel size (1024×768) both across anddown.

In step S93, the control circuit 101 creates a correction impossibledistribution image B03, and then the operation proceeds to step S94. Thecorrection impossible distribution image B03 is created throughprocessing identical to that described earlier.

In step S94, the control circuit 101 culls some of the pixelsconstituting the correction impossible distribution image B03 to ¼ ofthe initial size both across and down so as to obtain a correctionimpossible distribution image b03 with a reduced size of 256×192 pixelsand also detects the smallest value among the values indicated in thecorrection impossible distribution image b03. In other words, thecontrol circuit 101 ascertains the smallest correction impossibledistribution value detected through the entire image.

In step S95, the control circuit-101 obtains through calculation atarget projection image JJ01 by multiplying the linearized image C01 bythe smallest value detected as described above and then the operationproceeds to step S96. In more specific terms, the control circuit 101obtains the image through calculation expressed as; (R_(JJ01), G_(JJ01),B_(JJ01))_(i)=(R_(C01)×R_(min), G_(C01)×G_(min), B_(C01)×B_(min))_(i).It is to be noted that (R_(min), G_(min), B_(min)) above represents thesmallest value.

In step S96, the control circuit 101 obtains through calculation atarget projection image KK01 resulting from reflectance correction bydividing the target projection image JJ01 by the reflectancedistribution image A03 and then the operation proceeds to step S97. Morespecifically, the control circuit 101 obtains the image throughcalculation expressed as; (R_(KK01), G_(KK01),B_(KK01))_(i)=(R_(JJ01)/R_(A03), G_(JJ01)/G_(A03),B_(JJ01)/B_(A03))_(i).

In step S97, the control circuit 101 obtains through calculation aprojection image LL01 by adding the ambient light pattern correctionimage FF01 to the target projection image KK01 resulting from thereflectance correction and then the operation proceeds to step S98. Inmore specific terms, the control circuit 101 obtains the image throughcalculation expressed as; (R_(LL01), G_(LL01),B_(LL01))_(i)=(R_(KK01)+R_(FF01), G_(KK01)+G_(FF01),B_(KK01)+B_(FF01))_(i).

In step S98, the control circuit 101 obtains the actual projection imageLL02 converted back to the nonlinear data format through γ conversionexecuted on the projection image LL01. The γ conversion should beexecuted by using an LUT stored in the flash memory 101B.

The following advantages are achieved through Variation 2 describedabove.

(1) The control circuit 101 assumes a uniform ambient light patterndistribution over the entire projection image plane based upon thelargest value indicated in the ambient light pattern distribution withthe altered data size and obtains through calculation correctioninformation (ambient light pattern correction image) based upon theuniform distribution value for each of specific areas defined on theprojection image plane. By assuming such uniformity in the ambient lightpattern distribution, the onus of the calculation processing is lessenedcompared to that of processing executed without assuming uniformity andconsequently, the processing can be executed within a shorter period oftime.

(2) The control circuit 101 assumes a uniform lowered brightnessdistribution through the entire projection image plane based upon thesmallest value indicated in the lowered brightness distribution with thealtered data size and executes the arithmetic operation needed forcorrection based upon the uniform lowered brightness distribution. Byassuming such uniformity in the lowered brightness distribution, theonus of the calculation processing is lessened compared to that ofprocessing executed without assuming uniformity and consequently, theprocessing can be executed within a shorter period of time.

A program enabling input image correction processing executed asdescribed above may be provided to the projector apparatus 1 as acomputer program product adopting any of various modes, e.g., via arecording medium such as the memory card 150 having the program recordedtherein and via the external interface (I/F) circuit 104 connected witha communication network.

The program enabling the control described above may be provided in arecording medium such as a CD-ROM or in data signals transmitted throughthe Internet or the like. FIG. 34 illustrates how the program may beprovided. A reproduction apparatus 200 receives the program via a CD-ROM300. The reproduction apparatus 200 is also capable of connecting with acommunication line 310. A computer 400 is a server computer thatprovides the program stored in a recording medium such as a hard disk.The communication line 310 may be the Internet or a communicationnetwork for personal computer communication, or it may be a dedicatedcommunication line. The computer 400 reads out the program from the harddisk and transmits the program to the reproduction apparatus 200 via thecommunication line 310. Namely, the program embodied as data signalscarried on a carrier wave can be transmitted via the communication line310. In other words, the program can be distributed as acomputer-readable computer program product assuming any of various modesincluding a recording medium and a carrier wave.

The above described embodiment is an example and various modificationscan be made without departing from the scope of the invention.

1. A projector apparatus, comprising: a projection unit that projects an image onto a projection surface; a reflectance distribution detection unit that detects a reflectance distribution at the projection surface; a density distribution detection unit that detects a density distribution of a base pattern on the projection surface; a smoothing unit that smooths the reflectance distribution and the density distribution; an input unit that inputs image data; a correction unit that corrects the input image data based upon the smoothed reflectance distribution and the smoothed density distribution; and a control circuit that controls the projection unit so as to project the image based upon the correction image data.
 2. A projector apparatus according to claim 1, wherein: the correction unit alters a data size of the density distribution to a size smaller than the data size of the image that the projection unit projects, and obtains through calculation correction information based upon the reflectance distribution and the density distribution with the altered data size, the correction information being used to cancel out an appearance of the base pattern on the projection surface.
 3. A projector apparatus according to claim 2, wherein: the correction unit also generates a possible/impossible distribution image based upon the correction information, the image data input from the input unit and the reflectance distribution, the possible/impossible distribution image indicating a distribution of areas where the appearance of the base pattern on the projection surface may or may not be cancelled out; the correction unit individually alters the data size of data constituting the possible/impossible distribution image and the data size of the input image data each to a size smaller than the data size of the image that the projection unit projects; and the correction unit corrects the input image data by using the possible/impossible distribution image with the altered data size, the input image with the altered data size, the reflectance distribution and the correction information.
 4. A projector apparatus according to claim 2, wherein: the correction unit obtains through calculation the correction information for each of specific areas defined on a projection image plane, based upon the density distribution with the altered data size.
 5. A projector apparatus according to claim 2, wherein: the correction unit adjusts the density distribution based upon a largest value indicated in the density distribution with the altered data size so as to achieve a uniform density distribution over an entire projection image plane, and obtains through calculation the correction information for each of specific areas defined on a projection image plane, based upon the uniform density distribution.
 6. A projector apparatus according to claim 3, wherein: the correction unit executes arithmetic operation needed for correction for each of specific areas defined on a projection image plane, based upon the possible/impossible distribution image with the altered data size.
 7. A projector apparatus according to claim 3, wherein: the correction unit adjusts the possible/impossible distribution based upon a smallest value indicated in the possible/impossible distribution with the altered data size so as to achieve a uniform possible/impossible distribution over an entire projection image plane and executes arithmetic operation needed for correction based upon the uniform possible/impossible distribution.
 8. A non-transitory, computer readable storage medium having included therein a projection image correcting program that can be executed on a computer, with the projection image correcting program enabling the computer to execute: detection processing through which a reflectance distribution at a projection surface is detected; density distribution detection processing through which a density distribution of a base pattern on the projection surface is detected; smoothing processing through which the reflectance distribution and the density distribution are smoothed; input processing through which image data are input; correction processing through which the input image data are corrected based upon the smoothed reflectance distribution and the smoothed density distribution; and projection processing through which an image based upon the correction image data is projected. 